The well known, three-piece, sheet metal, food container is fast being supplanted by a two-piece container having a seamless body with one end wall integral with the body and the other end wall secured to the body by means of a double seam after filling the container. Such containers for beer and soft drinks are made by the drawing and ironing process; whereas containers for fruits and vegetables which require a heavier and sturdier side wall are beginning to be made by a newer process known as draw/redraw.
Although the production of sheet metal containers by means of multiple draws is not new, the draw/redraw process is an improvement over the older drawing process in that it is done at higher speeds with greater draw ratios in each drawing step. Achieving this higher productivity-rate requires special machines and, inter alia, special lubricants for the metal-working operation; and to maintain this higher productivity-rate, subsequent processing steps to the formed container must also be at high speed or eliminated where possible.
U.S. Pat. No. 4,287,741 describes a class of citric acid esters which are effected as lubricants in the drawing and ironing process. We have found that the same citric acid esters are effective lubricants in the draw/redraw process described in relation to the present invention.